Studio dell'andamento temporale delle pressioni al fondo in un bacino di dissipazione a risalto

The paper deals with the statistical structure of temporal distribution of the turbulent pressure fluctuations at the bottom of the hydraulic jump, in order to define their influence on the stability of the linings in stilling basins. The researches into the statistical characteristic of the fluctuating pressure have been mainly limited to the study of the instantaneous spatial structure; recently, moving from these results, a design criterion for suitable floor slabs was presented. This criterion was made neglecting the inertia force in the instantaneous equilibrium of the forces acting on the slab. This assumption is corrected if the stability of the slab is assured by its weight only. In the case of slabs anchored with steel bars the inertial force must be considered in the instantaneous equilibrium of the slab since the force acting on the steel bars is proportional to the displacement of the slab. This force depends on the temporal distribution of the turbulent pressure also. Theoretical and experimental analyses are presented and the time of persistence of the pulsating pressure above a defined level and the maximum value of the pressure occurred in this time are defined. On the basin of these results, the limitations of the static criteria in the case of anchored structures are pointed out.